Book Excerpt: The Printed Circuit Designer’s Guide to... DFM Essentials, Ch. 1
October 25, 2024 | I-Connect007Estimated reading time: 1 minute

Excerpt from: The Printed Circuit Designer’s Guide to... DFM Essentials
By Anaya Vardya, American Standard Circuits / ASC Sunstone Circuits
Chapter 1: Materials
Standard Multilayer Materials
Most PCBs are manufactured using three basic materials: glass-reinforced epoxy laminate, prepreg, and copper foil. PCBs are constructed from three basic material types: copper foil, prepreg, and cores.
Copper foil: Sheets of copper foil are incorporated into the outer layer of the PCB, laminating it onto the prepreg to create the outer layers. Outer layers are generally constructed using ½-ounce copper or thicker depending on the design requirements. Internal layers are constructed with copper that is specified on the fabrication print. Half-ounce copper foil is commonly used for signal layers; 1 ounce for plane layers, and 2 ounce or greater for power planes where there is a high DC current. Other thicknesses may be used based on the design requirements.
Prepreg: This is a semi-cured glass resin material. The resin used for the FR-4 type materials is epoxy-based. There is no copper attached to this material.
Core: This is fully cured glass-resin material with copper laminated to both sides. This is typically used for internal layers. It is occasionally used for outer layers, but that is not a preferred construction method. A core is constructed from either one sheet of prepreg (single ply) or two or more sheets of prepreg, and two layers of copper foil. Single ply is considered the preferred core construction and has better dimensional stability.
High-frequency (RF/Microwave) Materials
High-frequency designs (1 GHz and up) require materials with closely controlled dielectric constants and dissipation factors. The FR-4 materials normally used for PCBs don’t have the desired controlled characteristics. The substrate materials used for high-frequency applications were originally based upon PTFE resin formulations that have the desired properties, i.e. dielectric constant (Dk) controlled to +/- 0.04 and dissipation factor (Df) to 0.0004. These values may vary somewhat depending on the material type and supplier. Today, there are a number of materials on the market that do not contain PTFE resin but still have controlled values that can be used for high-frequency applications.
Visit the I-Connect007 library to continue reading The Printed Circuit Designer’s Guide to... DFM Essentials.
Testimonial
"We’re proud to call I-Connect007 a trusted partner. Their innovative approach and industry insight made our podcast collaboration a success by connecting us with the right audience and delivering real results."
Julia McCaffrey - NCAB GroupSuggested Items
Trouble in Your Tank: Implementing Direct Metallization in Advanced Substrate Packaging
09/15/2025 | Michael Carano -- Column: Trouble in Your TankDirect metallization systems based on conductive graphite are gaining popularity throughout the world. The environmental and productivity gains achievable with this process are outstanding. Direct metallization reduces the costs of compliance, waste treatment, and legal issues related to chemical exposure. A graphite-based direct plate system has been devised to address these needs.
Closing the Loop on PCB Etching Waste
09/09/2025 | Shawn Stone, IECAs the PCB industry continues its push toward greener, more cost-efficient operations, Sigma Engineering’s Mecer System offers a comprehensive solution to two of the industry’s most persistent pain points: etchant consumption and rinse water waste. Designed as a modular, fully automated platform, the Mecer System regenerates spent copper etchants—both alkaline and acidic—and simultaneously recycles rinse water, transforming a traditionally linear chemical process into a closed-loop system.
Driving Innovation: Depth Routing Processes—Achieving Unparalleled Precision in Complex PCBs
09/08/2025 | Kurt Palmer -- Column: Driving InnovationIn PCB manufacturing, the demand for increasingly complex and miniaturized designs continually pushes the boundaries of traditional fabrication methods, including depth routing. Success in these applications demands not only on robust machinery but also sophisticated control functions. PCB manufacturers rely on advanced machine features and process methodologies to meet their precise depth routing goals. Here, I’ll explore some crucial functions that empower manufacturers to master complex depth routing challenges.
Trouble in Your Tank: Minimizing Small-via Defects for High-reliability PCBs
08/27/2025 | Michael Carano -- Column: Trouble in Your TankTo quote the comedian Stephen Wright, “If at first you don’t succeed, then skydiving is not for you.” That can be the battle cry when you find that only small-diameter vias are exhibiting voids. Why are small holes more prone to voids than larger vias when processed through electroless copper? There are several reasons.
The Government Circuit: Navigating New Trade Headwinds and New Partnerships
08/25/2025 | Chris Mitchell -- Column: The Government CircuitAs global trade winds continue to howl, the electronics manufacturing industry finds itself at a critical juncture. After months of warnings, the U.S. Government has implemented a broad array of tariff increases, with fresh duties hitting copper-based products, semiconductors, and imports from many nations. On the positive side, tentative trade agreements with Europe, China, Japan, and other nations are providing at least some clarity and counterbalance.